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"I would never die for my beliefs because I might be wrong."

-- Bertrand Russell


Nov
29
answered Why is Physics so hard?
Nov
28
comment Searching books and papers with equations
@Lagerbaer, not a bad suggestion, but the problem is that there are so many idiosyncratic notations that you might miss what you are looking for just because someone wants to write his derivatives in "Newtonian fluxions" style instead of Leibniz notation or whatever. And just the problem of different names for the relevant variables is daunting enough.
Nov
28
comment Searching books and papers with equations
On the other hand, for integer sequences, there is a nice website cataloguing them: oeis.org . I wish someone would think up something like that for formula's. Maybe I should think about it.
Nov
28
comment Searching books and papers with equations
Nice question. Honestly, I don't know how to do it either. I just try to associate keywords I think are relevant. And I just play around until I find what I need. Or not. But one thing is certain, the search can be interesting in itself. Sometimes, I wasn't able to find out what I needed, but I still harvested all kinds of interesting articles.
Nov
28
revised Measuring the speed of light and defining the metre - absolute or relative?
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Nov
28
answered Measuring the speed of light and defining the metre - absolute or relative?
Nov
28
comment Is there a theory about kinetic energy “particles”?
When you bombard electrons with photons, you are in effect giving them kinetic energy. All particles are "kinetic energy particles". There's no need for an extra kind of particles. A change in kinetic energy corresponds to work being exerted by or on the system.
Nov
28
comment Four-dimensionalism vs energy economy
Never heard of it. Unless it means: the universe can be described as a 4-dimensional manifold, then it is a part of for instance GR or quantum field theory, but in and of itself, it is not rich enough to constitute a physical theory.
Nov
28
comment Four-dimensionalism vs energy economy
Not sure this is even a physics question. Remember however there is a holographic principle stating that all information in a N-dimensional space can be encoded on a (N-1)-dimensional boundary. If that principle holds true, I don't see any problem.
Nov
27
comment Best example of energy-entropy competition?
I'd say all living organisms seem to enter this cathegory. But it's hard to prove quantitatively. But obviously, when we eat, we don't do so to increase our energy (except when growing), we eat to diminish or keep our entropy low.
Nov
27
revised Is there a difference between observing a particle and hitting it with another particle?
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Nov
27
answered Is there a difference between observing a particle and hitting it with another particle?
Nov
27
comment If the light velocity is a vector quantity, why vector addition cannot be applied to it?
You can also mention that there is a kind of adapted addition law.
Nov
26
comment Did Einstein prove $E=mc^2$ correctly?
OK, I never meant to start a flame war. I have adapted my reply, I changed the "lousy" to "not great" and I have stricken the Hilbert comment and refered to Marek's reply. Everybody happy now? ;p
Nov
26
revised Did Einstein prove $E=mc^2$ correctly?
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Nov
24
revised Did Einstein prove $E=mc^2$ correctly?
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Nov
24
comment Did Einstein prove $E=mc^2$ correctly?
Well, how can I address it properly if I don't know what Ohanian is saying? So, thank's for the link.
Nov
24
answered Did Einstein prove $E=mc^2$ correctly?
Nov
23
comment Rope tension question
Yeah, I think Mark is right. That, or I'm always explaining it incorrectly to students. Please, don't say I screwed up so bad. :p
Nov
22
comment Linearity of quantum mechanics and nonlinearity of macroscopic physics
You start with a huge mistake. Newton's equation of motion is in general non-linear. Only for special cases such as the harmonic oscillator is the equation linear. Take for instance Newton's equation for the Kepler problem (two gravitating masses) and see if you can combine two solutions linearly to obtain a new one. It is however correct that linear equations will never lead to chaos, but that doesn't mean that linear equations can't be difficult. As you correctly point out, quantum systems have exponentially more variables as compared to their classical counterparts.